364 SUMMARY OF CURRENT RESEARCHES RELATING TO 



dependent upon the width and walls of the vessel. Distinction must 

 be clearly drawn between (1) thyloses due to wounding, which are some- 

 times found in plants, where they do not occur normally, and which 

 only perform the role of preventing the drying-up of the wall of the 

 vessel, and (2) those normal thyloses due to the outgrowth of the pit- 

 membrane, which diminish the breadth of the vessel, thus increasing 

 capillarity and promoting the rise of water. Thyloses are often used in 

 connection with the storage of starch, and they may act as haustoria in 

 removing certain nourishing salts from the water ; further, they assist 

 in bringing certain carbohydrates into solution. The author considers 

 that physical factors are the cause of thylose-formation, and disagrees 

 with those writers who refer them to chemical causes. There is no 

 support for those who regard them as unicellular, for in large vessels, 

 especially in the roots, division-walls have been seen. The thyloses of 

 the roots are first formed in the youngest parts, while in the stem they 

 are first formed in the older vessels. In both cases their presence 

 depends upon certain anatomical and biological conditions. 



Phylloclades of Ruscus.* — J. Bernatsky has examined the phyllo- 

 clades of Ruscus, and finds that at the base is a central cylinder 

 consisting of several vascular bundles, the xylem of which is centrally 

 directed. In the upper part the central cylinder is merged into several 

 smaller cylinders having a similar orientation of xylem and phloem. 

 The portion which bears the inflorescence possesses not only single 

 vascular bundles but also a small central cylinder composed of two 

 bundles, which also have their xylems turned towards one another. 

 Thus the phylloclade must be a " canlome," for a central cylinder is 

 never found in any part of a leaf. 



Reproductive. 



Embryo-formation of Gunnera.f — J. Modilewski has studied the 

 embryo-sac formation of Gunnera chilmsis, and finds that the arche- 

 sporial cell develops directly into an embryo-sac without any inter- 

 mediate divisions. The first nucleus of the embryo-sac divides 

 regularly four times to form sixteen nuclei, four of which are in the 

 micropylar end and the remaining twelve in the antipodal end of the 

 embryo-sac. The ripe embryo-sac consists of a normal egg-apparatus, 

 six antipodals, and a cluster of central nuclei, which fuse to form a 

 large secondary embryo-sac nucleus. There is no suspensor, and the 

 embryo is imbedded in much endosperm. Embryo-formation is 

 probably parthenogenetic. 



Fertilisation of the Poppy 4 — P. Becquerel has studied the fertilisa- 

 tion of two varieties of Poppy, viz. Mephisto and Danebrog. The 

 experiments were carried out upon two groups of buds — the first 

 comprising unopened buds with bent peduncles, and stamens not yet 

 open ; the second group included older buds, where the peduncles were 



* Math. u. Naturwiss. Ber. Ungarn, xxi. (1907) pp. 113-18. See also Bot. Zeit., 

 lxvii. (1909) p. 23. 



+ Ber. Deutsch. Bot. Gesell., xxvia (1908) pp. 550-5 (1 pi.). 

 X Comptes Rendus, cxlviii. (1909) pp. 357-9. 



